<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js的变量</title>
</head>
<body>
<script>
  var a;
  console.log(a);
  var b=1;
  console.log(b);
  var c,d;
  console.log(c, d);
  var e=3.14,f=true,g="yyy";
  console.log(e, f, g);
</script>
</body>
</html>